Five jobs inside the machine
The parts may look different, but each one solves a clear problem.
Store or receive water
Reservoir machines carry their own supply. Plumbed machines receive water from the building and normally depend on suitable filtration and line pressure.
Move the water
A vibration pump, rotary pump or manual lever provides the energy that moves water through the brew circuit. Pump type changes sound and feel more reliably than it predicts taste.
Control the heat
A boiler, heat exchanger, thermoblock or thermocoil brings water into a useful brewing range. Temperature control and thermal mass determine how the system behaves between shots.
Route and release
Valves direct water to the group. On many pump machines, a three-way valve also releases pressure and drains residual water when brewing stops.
Meet the coffee
The group, shower screen, basket and prepared puck turn a pressurised water supply into a controlled brewing path. The basket is where machine design meets preparation.
The gauge is only reporting one location
A pressure gauge is useful, but it is not a live window into every part of the coffee bed. Depending on the machine, it may report pump pressure, brew-circuit pressure or boiler pressure. Read the machine manual before treating a number on the dial as pressure at the puck.
That is also why a familiar number cannot rescue a poor puck. Grind, dose, basket, distribution and coffee condition determine the resistance the water encounters.
- No flow: check water supply, grind and dose before assuming a pump fault.
- Very fast flow: look at grind, dose and puck preparation before adjusting the machine.
- Water after the shot: distinguish normal discharge into the drip tray from a leak.
- Changing sound: compare it with the manual and stop if water supply is uncertain.
Where designs genuinely differ
Pump or lever
Pumps aim for repeatable delivery. Levers make pressure part of the physical brewing motion. Neither label alone tells you whether a machine suits your routine.
One path or separate jobs
Single boilers share one heater between brew water and steam. Heat exchangers and dual boilers separate the jobs in different ways. Thermoblocks heat water as it travels.
How heat reaches the basket
E61-style, saturated, heated and compact groups manage temperature differently. Warm-up behaviour matters more at home than the prestige of a group name.
Geek level: what the three-way valve changes
On many pump machines, a three-way solenoid valve opens the brew path while the shot runs, then changes state when brewing stops. This relieves pressure from the group and routes residual water toward the drip tray. That is why a wet discharge after the shot can be normal, and why a blind basket can be used for backflushing only on machines designed for it.
Machines without that valve can behave differently after the shot. Never assume one cleaning method applies to every espresso machine.
Source notes
These references support the system and safety claims. Your exact equipment manual remains authoritative for operation and maintenance.